Multi-stepped motor vehicle transmissions or gearboxes having an input shaft, a first and a second intermediate shaft and an output shaft are well known in the art, see e.g. German patent specification 33 20 494, German published patent application 41 36 455 and German published patent application 41 16 189.
In the prior art transmission as disclosed in German patent specification 33 20 494 the arrangement of the input shaft and of the second intermediate shaft is conventional because two toothed wheels each (for the lower four forward gears) are designed as fixed wheels, whereas two further toothed wheels are designed as loose toothed wheels and are arranged on the two mentioned shafts to operate as gearshift wheels. The term "fixed wheel" shall hereinafter mean a toothed wheel being rigidly arranged on a shaft whereas the term "loose wheel" shall mean a toothed wheel being loosely journaled on a shaft but may be rigidly connected to that shaft by means of a gearshift sleeve as is well known to a person of ordinary skill. In the prior art transmission the reverse gear function is associated to the first intermediate shaft. For that purpose the first intermediate shaft carries two loose toothed wheels which, by means of a supplemental gearshift sleeve may be drivingly connected with each other but still being loosely journaled on the first intermediate shaft. These two loose toothed wheels on the first intermediate shaft each mesh with a loose toothed wheel on the input shaft and on the second intermediate shaft, respectively, namely with the loose toothed wheel associated to the third forward gear on the input shaft and with the loose toothed wheel associated to the first forward gear on the second intermediate shaft, respectively. Additionally, this prior art transmission is provided with a pair of toothed wheels constituting a fifth forward gear and being arranged on the input shaft and on the second intermediate shaft, respectively.
This prior art has a reduced axial length, as compared with still older transmission designs having all five forward gears and the reverse gear of a five gear transmission on two transmission shafts in parallel toothed wheel planes each.
The prior art transmission necessitates a total of four gearshift sleeves. A first gearshift sleeve being displaceable in two gearshift directions for the third and the fourth forward gear is provided on the input shaft. A second gearshift sleeve being also displaceable in two gearshift directions for the first and the second forward gear is provided on the second intermediate shaft. One further gearshift sleeve being displaceable only in one gearshift direction for the fifth forward gear is also arranged on the second intermediate shaft. A fourth gearshift sleeve being also displaceable only in one gearshift direction for the reverse gear is arranged on the first intermediate shaft, as already mentioned above.
Another prior art multi-stepped motor vehicle transmission having at least two intermediate shafts is disclosed in German disclosure document 41 36 455. This prior art transmission is a six-gear transmission. For engaging one of the six forward gears three distinct gearshift sleeves are provided being each displaceable in two gearshift directions, whereas one more gearshift sleeve, being displaceable only in one gearshift direction, is provided for engaging the reverse gear.
It is, therefore, an object underlying the invention to improve a multi-stepped motor vehicle transmission as mentioned at the outset such that the number of gearshift sleeves is reduced to a minimum and the design complexity as well as the dimensions are also reduced to a minimum, yet having a maximum of forward gears and a reverse gear, all being synchronized and being adapted to be engaged individually.